I know nothing about software or game development.

I think it would depend on how old, how motivated and how interested the kid is. Never in history has there ever been a time when we've had this much free resource immediately available to us. My cousin started his son on learning game development at about 11 or 12. He learned coding, used online resources and video courses and pretty much self-taught in the way any student would learn in a programming course. He's making simple Android games and he's been happy jumping on the deep and and doing it "properly".